156
FXUS21 KWNC 041930
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 04 2024
SYNOPSIS: EARLY IN WEEK-2, AMPLIFIED MID-LEVEL LOW PRESSURE IS FORECAST TO MOVE
ACROSS THE CENTRAL CONTIGUOUS U.S. (CONUS) FAVORING ELEVATED CHANCES OF
ENHANCED PRECIPITATION DOWNSTREAM ACROSS PARTS OF THE MISSISSIPPI VALLEY AND
SOUTHEAST. ANOTHER AREA OF MID-LEVEL LOW PRESSURE IS FORECAST TO MOVE SOUTHWARD
FROM THE GULF OF ALASKA TO THE NORTHWESTERN CONUS BRINGING ADDITIONAL ROUNDS OF
HEAVY PRECIPITATION (HIGH ELEVATION SNOW) TO PARTS OF THE PACIFIC NORTHWEST AND
ROCKIES, ALTHOUGH THERE ARE SOME TIMING DIFFERENCES IN THE MODELS. A STRONG
PRESSURE GRADIENT MAY LEAD TO ENHANCED OFFSHORE FLOW AND INCREASED WIND SPEEDS
ACROSS PARTS OF CALIFORNIA AT THE START OF THE PERIOD. UNSETTLED WEATHER MAY
RETURN TO PARTS OF WESTERN ALASKA FOLLOWING A BRIEF LULL IN ACTIVITY EARLY IN
WEEK-2.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS, MIDDLE AND LOWER MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND THE
SOUTHEAST, TUE-THU, NOV 12-14.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST,
TUE-THU, NOV 12-14.
SLIGHT RISK OF HEAVY SNOW ACROSS NORTHERN PORTIONS OF THE CASCADES, TUE-THU,
NOV 12-14.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE ROCKIES, TUE-MON, NOV 12-18.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE PACIFIC NORTHWEST, NORTHERN
ROCKIES, AND THE HIGH PLAINS, TUE-MON, NOV 12-18.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF CALIFORNIA, TUE-WED, NOV 12-13.
SLIGHT RISK OF HIGH WINDS ACROSS COASTAL PORTIONS OF SOUTHEAST ALASKA, TUE, NOV
12.
SLIGHT RISK OF HIGH WINDS ACROSS COASTAL PORTIONS OF SOUTHWESTERN MAINLAND
ALASKA AND THE ALEUTIANS, THU-SAT, NOV 14-16.
DETAILED SUMMARY
FOR THURSDAY NOVEMBER 07 - MONDAY NOVEMBER 11:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY NOVEMBER 12 - MONDAY NOVEMBER 18: SHORTWAVE MID-LEVEL TROUGHING IS
FORECAST TO DIG ACROSS THE INTERIOR WEST AND GRADUALLY WEAKEN AS IT PROGRESSES
EASTWARD ACROSS THE CONUS DURING THE FIRST HALF OF WEEK-2. HOWEVER, A FAVORABLE
BAROCLINIC ENVIRONMENT IS LIKELY TO EXIST AHEAD OF THIS FEATURE AS A RESULT OF
ENHANCED RIDGING OVER EASTERN NORTH AMERICA. THIS LEADS TO INCREASED
PRECIPITATION CHANCES OVER A BROAD AREA OF THE EAST-CENTRAL CONUS, WITH THE
ECENS PROBABILISTIC EXTREMES TOOL (PET) DEPICTING MANY AREAS HAVING AT LEAST A
30 PERCENT CHANCE OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE AND 1-INCH EARLY IN THE PERIOD. THE GEFS PET IS NOT
AS ROBUST, WITH PROBABILITIES GREATER THAN 20 PERCENT FOR 3-DAY PRECIPITATION
TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE OVER PARTS OF THE OHIO AND
TENNESSEE VALLEYS AND LIMITED COVERAGE FOR TOTALS REACHING 1-INCH. GIVEN THE
SIMILAR SYNOPTIC SET-UP IN THE MODELS, A SLIGHT RISK OF HEAVY PRECIPITATION IS
POSTED ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, MIDDLE AND LOWER
MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND THE SOUTHEAST, NOV 12-14. SOME OF
THIS MOISTURE MAY SHIFT INTO PARTS OF THE NORTHEAST BY THE MIDDLE OF THE
PERIOD, BRINGING WELCOMING RAINFALL FOLLOWING LITTLE TO NO RAINFALL DURING THE
MONTH OF OCTOBER.
ANOTHER TROUGH IS FORECAST TO DROP SOUTHWARD FROM THE GULF OF ALASKA TO THE
WEST COAST OF THE CONUS AT THE BEGINNING OF WEEK-2. THE 0Z GEFS AND CMCE DEPICT
A MORE AMPLIFIED TROUGH REACHING THE WEST COAST, WHILE THE 0Z ECENS KEEPS THE
FEATURE WEAKER INITIALLY. HOWEVER, ALL OF THE MODELS INDICATE THIS THROUGH
BECOMING MORE STATIONARY ACROSS THE ROCKIES WITH INCREASING NEGATIVE MID-LEVEL
HEIGHT ANOMALIES LATER IN WEEK-2. THE 0Z GEFS DEPICTS ELEVATED CHANCES FOR
ENHANCED INTEGRATED VAPOR TRANSPORT (IVT) ALONG THE WEST COAST EARLY IN WEEK-2,
CORRESPONDING WITH THE ARRIVAL OF THE TROUGH. ADDITIONALLY, BOTH THE GEFS AND
ECENS PETS INDICATE AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION TOTALS
EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 1.5-INCHES OVER COASTAL AREAS OF
THE PACIFIC NORTHWEST. AS A RESULT A SLIGHT RISK OF HEAVY PRECIPITATION IS
HIGHLIGHTED ACROSS THE REGION, NOV 12-14. AN ACCOMPANYING SLIGHT RISK FOR HEAVY
SNOW IS POSTED ACROSS NORTHERN PARTS OF THE CASCADES WHERE THE UNCALIBRATED
ECENS DEPICTS PROBABILITIES GREATER THAN 20 PERCENT FOR 3-DAY SNOWFALL TOTALS
GREATER THAN 6-INCHES. AS THIS TROUGH SHIFTS FURTHER INLAND OVER THE ROCKIES
AND SLOWS DOWN, CHANCES INCREASE FOR PERIODIC DISTURBANCES TO BRING ENHANCED
CHANCES FOR HEAVY SNOW ACROSS THE REGION. WHILE EXACT TIMING AND PLACEMENT OF
THE HEAVIEST SNOWFALL IS UNCERTAIN, THE GEFS PET SUPPORTS A SLIGHT RISK FOR
HEAVY SNOW ACROSS THE ROCKIES FOR ALL OF WEEK-2, WITH INCREASED COVERAGE FOR
3-DAY SNOW WATER EQUIVALENT (SWE) TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE AND 0.5 INCHES (ONE INCH LOCALLY). ELEVATED WIND SPEEDS ARE ALSO
POSSIBLE ASSOCIATED WITH THE TROUGH, WITH A SLIGHT RISK OF HIGH WINDS
STRETCHING FROM THE PACIFIC NORTHWEST THROUGH THE NORTHERN ROCKIES AND HIGH
PLAINS FOR ALL OF WEEK-2, SUPPORTED BY THE ECENS PET.
SURFACE HIGH PRESSURE OVER THE EASTERN PACIFIC AND EXTENDING OVER THE GREAT
BASIN EARLY IN THE PERIOD COMBINED WITH LOWER PRESSURE OVER THE DESERT
SOUTHWEST FAVOR A TIGHT PRESSURE GRADIENT ACROSS CALIFORNIA. THE UNCALIBRATED
0Z GEFS AND ECENS DEPICT ELEVATED CHANCES FOR WIND SPEEDS EXCEEDING 20-KNOTS
OFF THE CALIFORNIA COAST AND IT IS FEASIBLE THAT THESE WINDS EXTEND INLAND OVER
SOME AREAS GIVEN THE PREDICTED OFFSHORE FLOW. THEREFORE, A SLIGHT RISK FOR HIGH
WINDS IS POSTED ACROSS PARTS OF CALIFORNIA, NOV 12-13.
ACROSS ALASKA, DEPARTING TROUGHING AND ASSOCIATED SURFACE LOW PRESSURE MAY
BRING ENHANCED WINDS TO PARTS OF COASTAL SOUTHEASTERN ALASKA AT THE OUTSET OF
THE PERIOD, SUPPORTING A SLIGHT RISK FOR HIGH WINDS ON NOV 12. RIDGING IS
FORECAST TO BUILD OVER THE NORTHEAST PACIFIC IN THE WAKE OF THIS SYSTEM, WITH
POSITIVE MID-LEVEL HEIGHT ANOMALIES EXTENDING THROUGH EASTERN ALASKA FAVORING A
BRIEF PERIOD OF MORE TRANQUIL WEATHER. HOWEVER, ADDITIONAL TROUGHING AND
SURFACE LOW PRESSURE FORECAST TO MOVE OVER THE BERING SEA MAY ONCE AGAIN BRING
PERIODS OF UNSETTLED WEATHER TO WESTERN ALASKA BY THE MIDDLE OF THE PERIOD.
GIVEN THIS POTENTIAL, ANOTHER SLIGHT RISK FOR HIGH WINDS IS HIGHLIGHTED ACROSS
COASTAL PORTIONS OF SOUTHWESTERN MAINLAND ALASKA AND THE ALEUTIANS, NOV 14-16.
FORECASTER: THOMAS COLLOW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page